River Song's World was an alternate timeline created by river song when she altered a fixed point in time by preventing the Doctor's death. In this timeline all of earth's history occured simultaneously the war of the roses entered its second year, dinosaurs walked the earth and Winston Churchill was the leader of the holy roman empire.
History
On April 22 2011 the Doctor meet River Song (who was wearing an astronaut suit) at Lake Silencio on planet earth. He told her that he knew she was the one that was going to kill him and that he forgave her. River however drained the suit of its power supply making it impossible for her to kill the Doctor and created the new timeline. (DW: The Wedding of River Song)